I made a lager last weekend, and during the week the temp went out of control due to our wonderful winter weather. 60f on February 1st in NYC, where normal is 35. Anyway, the beer also got warmer than I wanted. I noticed the gases coming off smelled slightly sour after that.

Today is day 7 of fermentation so I took a reading today, it went from an OG of 1.052 down to 1.015, so that isn't a problem. But it has a lot of off tastes to it. I think I detect diacetyl, even my 85 year old mother thought it had a slippery feel in the mouth. But it is also somewhat sour, something I'd never tasted in my beers at this point. My starter didn't smell like that so the yeast was good. My sanitation techniques are pretty solid.

Is this batch toast? I've brought it inside the house for a diacetyl rest, and I'll let it finish fermenting. I'll also put it in the secondary and let it lager, but after that step if it still tastes like that I may not bother to bottle.

Are you seriously considering dumping a lager because of off-flavors 7 DAYS into fermentation??? Dude, seriously, chill.

We don't lager these kinds of beers just because we're stubborn. We do it because they don't taste right for the first few weeks of life. If they tasted good after 7 days, then who in their right mind would lager then for months on end?

Don't stress it at this point. "Sour" isn't the most common flavor, but I've never bothered sampling a lager this young. Finish the primary for a few days for diactyl cleanup, then lager it for a month or so. If its not improving at that point, you might have a problem, but will need another month of lagering to tell for sure.

I had my first lager taste sour after 3 weeks at 47 degree primary when I drank the hydrometer draw. I tasted it after 6 weeks in primary yesterday just before transferring it to the lagering stage and it tasted awesome, exactly as intended during recipe design. I guess lagers just taste sour when young.

As I said, I'm still going through with it, so I'm not THAT crazy to dump it yet. I've done lagers before and I'd never had anything taste like this. It usually goes from raw, to tasty, and then to incredible.

I'll give it a month or two from this point, and hold off on final judgement until then.

Gave it another taste tonight from the hydrometer flask. As soon as I removed the airlock I knew that I was OK.

It cleaned itself up nicely, although it is still a tad sweet for a lager at this point. A month or so at 32-36 should clean it up and clarify it. This is by far the lightest color beer I've ever made, as light as a Bud. It is also my first all-grain so I'm psyched that it won't have that extract twang, although this tasting didn't seem all that different than any extract brew at this point.

My OG was 1.052, and it was 1.012 tonight, so over 75% attenuation at this point. Pretty good. I need to transfer to the secondary to get it into the cold, in the meantime it'll go back in my cool room.

That beer is extremely green. The sour taste you are experiencing is probably sulphurous acid from SO2 still dissolved in the beer from the primary fermentation. As ghpeel has suggested, slow down and give this beer the time it needs. It is nowhere near being done.

Gave it another taste tonight from the hydrometer flask. As soon as I removed the airlock I knew that I was OK.

It cleaned itself up nicely, although it is still a tad sweet for a lager at this point. A month or so at 32-36 should clean it up and clarify it. This is by far the lightest color beer I've ever made, as light as a Bud. It is also my first all-grain so I'm psyched that it won't have that extract twang, although this tasting didn't seem all that different than any extract brew at this point.

My OG was 1.052, and it was 1.012 tonight, so over 75% attenuation at this point. Pretty good. I need to transfer to the secondary to get it into the cold, in the meantime it'll go back in my cool room.